In order to manage plans, you have to be logged in as the system owner. Resellers can be accessed at
Right top account dropdown > Admin > Plans.
With plans you can define which parts of the platform are visible for a user. For some components you can set a maximum allowed amount of items.
By default, every user starts with a free plan. A free plan has no permission to do anything. This free plan can not be managed and exists for all resellers.